The principal objective of the proposed research is development of comprehensive and quantitative means for assessment of dyskinetic impairments in psychiatric patients treated with neuroleptics. Numerous studies in the past have explored the potential value of a number of techniques, but they have not generally provided an exhaustive or systematic investigation of specific aspects of dyskinesias. We have developed a new technique for assessment of the force control in dyskinetic subjects. The technique consists of recording the patient's capacity in dyskinetic subjects. The technique consists of recording the patient's capacity to maintain steady pressure on an isometric task at specified levels of force. It has been adapted to assess force control in each extremity and in the oro-mandibular region. Specific studies in this proposal will: a) establish the degree of impairment characterizing voluntary movements and force control in neuroleptic-treated psychotic patients (with and without dyskinetic impairment); b) establish intraindividual differences in dyskinetic impairment in the extremities nad oromandibular region, and c) extract indices of validity and reliability of these measures. These objectives are to be accomplished with two closely related techniques. One will extract information on a subject's capacity for sustained force control, and the other will investigate dynamic force control during voluntary movement in tracking tasks. We will address questions that center around attributes that characterize force control mechanisms during sustained and dynamic changes of motor output. Among these questions are: a) Is tardive dyskinesia a generalized motor disorder which is reflected in all tasks and under all loads, or is it related to dysfunction of specific bands of neuro-motor units? b) Are there differences between sustained and dynamic force control functions which can contribute to description and localization of dyskinetic impairment? c) Can the objective indicators obtained from this research be instrumental in specifying clinically relevant categories related to severity of TD (mild, moderate, severe), and related to nature of TD (transient, withdrawal, persistent)? d) Are force control indices sensitive to changes in drug treatment?